1. Field of the Invention
The invention relates in general to a chip structure and a process for forming the same. More particularly, the invention relates to a chip structure for improving the resistance-capacitance delay and a forming process thereof.
2. Description of the Related Art
Nowadays, electronic equipment are increasingly used to achieve many various tasks. With the development of electronics technology, miniaturization, multifunction task, and comfort of utilization are among the principle guidelines of electronic product manufacturers. More particularly in semiconductor manufacture process, the semiconductor devices with 0.18 microns have been mass-produced. However, the relatively fine interconnections therein negatively impact the chip. For example, this causes the voltage drop of the buses, the resistance-capacitor delay of the key traces, and noises, etc.
FIG. 1 is a cross-sectional view showing a conventional chip structure with interconnections.
As shown in FIG. 1, a chip structure 100 is provided with a substrate 110, an built-up layer 120 and a passivation layer 130. There are plenty of electric devices 114, such as transistors, on a surface 112 of the substrate 110, wherein the substrate 110 is made of, for example, silicon. The built-up layer 120 provided with a dielectric body 122 and an interconnection scheme 124 is formed on the surface 112 of the substrate 110. The interconnection scheme 124 interlaces inside the dielectric body 122 and is electrically connected to the electric devices 114. Further, the interconnection scheme 124 includes many conductive pads 126 exposed outside the dielectric body 122 and the interconnection scheme 124 can electrically connect with external circuits through the conductive pads 126. The dielectric body 122 is made of, for instance, silicon nitride or silicon oxide. In addition, the passivation layer 130 is deposited on the built-up layer 120, and has many openings respectively exposing the conductive pads 126. The interconnection scheme 124 includes at least one metal layer that can serve as a power bus or a ground bus. The power bus or the ground bus is connected to at least one of the conductive pads 126 through which the power bus or the ground bus can electrically connect with external circuits.
However, as far as the chip structure 100 is concerned, resistance-capacitance (RC) delay is easily generated because the line width of the interconnection scheme 124 is extremely fine, about below 0.3 microns, the thickness of the interconnection scheme 124 is extremely thin, and the dielectric constant of the dielectric body 122 is extremely high, about 4. Therefore, the chip efficiency drops off. In particular, the RC delay even usually occurs with respect to a power bus, a ground bus or other metal lines transmitting common signals. In addition, the production of the interconnection scheme 124 with extremely fine line width is necessarily performed using facilities with high accuracy. This causes production costs to dramatically rise.
The present invention is related to a R.O.C. patent application Ser. No. 88120548, filed Nov. 25, 1999, by M. S. Lin, issued Sep. 1, 2001, now R.O.C. Pat. No. 140721. R.O.C. patent application Ser. No. 88120548 claims the priority of pending U.S. patent application Ser. No. 09/251,183 and the subject matter thereof is disclosed in pending U.S. patent application Ser. No. 09/251,183. The present invention is related to a R.O.C. patent application Ser. No. 90100176, filed Jan. 4, 2001, by M. S. Lin and J. Y. Lee, now pending. The subject matter of R.O.C. patent application Ser. No. 90100176 is disclosed in pending U.S. patent application Ser. No. 09/691,497. The present invention is related to a Japanese patent application Ser. No. 200156759, filed Mar. 1, 2001, by M. S. Lin and J. Y. Lee, now pending. The present invention is related to a European patent application Ser. No. 01480077.5, filed Aug. 27, 2001, by M. S. Lin and J. Y. Lee, now pending. The present invention is related to a Singaporean patent application Ser. No. 200101847-2, filed Mar. 23, 2001, by M. S. Lin and J. Y. Lee, now pending. Japanese patent application Ser. No. 200156759, European patent application Ser. No. 01480077.5, and Singaporean patent application Ser. No. 200101847-2 claim the priority of pending U.S. patent application Ser. No. 09/691,497 and the subject matter of them is disclosed in pending U.S. patent application Ser. No. 09/691,497.
Accordingly, an objective of the present invention is to provide a chip structure and a process for forming the same that improves resistance-capacitance delay and reduces energy loss of the chip.
Another objective of the present invention is to provide a chip structure and a process for forming the same that can be produced using facilities with low accuracy. Therefore, production costs can substantially reduce.
To achieve the foregoing and other objectives, the present invention provides a chip structure that comprises a substrate, a first built-up layer, a passivation layer and a second built-up layer. The substrate includes many electric devices placed on a surface of the substrate. The first built-up layer is located on the substrate. The first built-up layer is provided with a first dielectric body and a first interconnection scheme, wherein the first interconnection scheme interlaces inside the first dielectric body and is electrically connected to the electric devices. The first interconnection scheme is constructed from first metal layers and plugs, wherein the neighboring first metal layers are electrically connected through the plugs. The passivation layer is disposed on the first built-up layer and is provided with openings exposing the first interconnection scheme. The second built-up layer is formed on the passivation layer. The second built-up layer is provided with a second dielectric body and a second interconnection scheme, wherein the second interconnection scheme interlaces inside the second dielectric body and is electrically connected to the first interconnection scheme. The second interconnection scheme is constructed from at least one second metal layer and at least one via metal filler, wherein the second metal layer is electrically connected to the via metal filler. The thickness, width, and cross-sectional area of the traces of the second metal layer are respectively larger than those of the first metal layers. In addition, the first dielectric body is constructed from at least one first dielectric layer, and the second dielectric body is constructed from at least one second dielectric layer. The individual second dielectric layer is thicker than the individual first dielectric layer.
According to a preferred embodiment of the present invention, the thickness of the traces of the second metal layer ranges from 1 micron to 50 microns; the width of the traces of the second metal layer ranges from 1 micron to 1 centimeter; the cross sectional area of the traces of the second metal layer ranges from 1 square micron to 0.5 square millimeters. The first dielectric body is made of, for example, an inorganic compound, such as a silicon nitride compound or a silicon oxide compound. The second dielectric body is made of, for example, an organic compound, such as polyimide (PI), benzocyclobutene (BCB), porous dielectric material, or elastomer. In addition, the above chip structure further includes at least one electrostatic discharge (ESD) circuit and at least one transitional device that are electrically connected to the first interconnection scheme. The transitional device can be a driver, a receiver or an I/O circuit. Moreover, the first interconnection scheme include at least one first conductive pad, at least one second conductive pad, and at least one linking trace, wherein the openings of the passivation layer expose the first conductive pad and the second conductive pad. The second conductive pad is electrically connected to the second interconnection scheme. The first conductive pad is exposed to the outside. The linking trace connects the first conductive pad with the second conductive pad and is shorter than 5,000 microns.
To sum up, the chip structure of the present invention can decline the resistance-capacitance delay, the power of the chip, and the temperature generated by the driving chip since the cross sectional area, the width and the thickness of the traces of the second metal layer are extremely large, since the cross sectional area of the via metal filler is also extremely large, since the second interconnection scheme can be made of low-resistance material, such as copper or gold, since the thickness of the individual second dielectric layer is also extremely large, and since the second dielectric body can be made of organic material, the dielectric constant of which is very low, approximately between 1xcx9c3, the practical value depending on the applied organic material.
In addition, the chip structure of the present invention can simplify a design of a substrate board due to the node layout redistribution, fitting the design of the substrate board, of the chip structure by the second interconnection scheme and, besides, the application of the fewer nodes to which ground voltage or power voltage is applied. Moreover, in case the node layout redistribution of various chips by the second interconnection scheme causes the above various chips to be provided with the same node layout, the node layout, matching the same node layout of the above various chips, of the substrate board can be standardized. Therefore, the cost of fabricating the substrate board substantially drops off.
Moreover, according to the chip structure of the present invention, the second interconnection scheme can be produced using facilities with low accuracy. Therefore, production costs of the chip structure can substantially be reduced.
To achieve the foregoing and other objectives, the present invention provides a process for making the above chip structure. The process for fabricating a chip structure comprises the following steps.
Step 1: A wafer is provided with a plurality of electric devices, an interconnection scheme and a passivation layer. Both the electric devices and the interconnection scheme are arranged inside the wafer. The interconnection scheme is electrically connected with the electric devices. The passivation layer is disposed on a surface layer of the wafer. The passivation layer has at least one opening exposing the interconnection scheme. The largest width of the opening of the passivation ranges from 0.5 microns to 200 microns
Step 2: A conductive layer is formed over the passivation layer of the wafer by, for example, a sputtering process, and the conductive layer is electrically connected with the interconnection scheme.
Step 3: A photoresist is formed onto the conductive layer, and the photoresist has at least one opening exposing the conductive layer.
Step 4: At least one conductive metal is filled into the opening of the photoresist by, for example, a electroplating process, and the conductive metal is disposed over the conductive layer.
Step 5: The photoresist is removed.
Step 6: The conductive layer exposed to the outside is removed by, for example, an etching process, and the conductive layer deposited under the conductive metal remains. A signal is transmitted from one of the electric devices to the interconnection scheme, then passes through the passivation layer, and finally is transmitted to the conductive metal, and further, the signal is transmitted from the conductive metal to the interconnection scheme with passing through the passivation layer, and finally is transmitted to the other one or more of the electric devices.
Provided that two metal layers are to be formed, the process for fabricating the above chip structure further comprises the following steps:
Step 7: A dielectric sub-layer is formed over the passivation layer and covers the formed conductive metal. The dielectric sub-layer has at least one opening exposing the conductive metal formed at a lower portion.
Step 8: At least other one conductive layer is formed on the dielectric sub-layer and into the opening of the dielectric sub-layer by, for example, a sputtering process. The other conductive layer is electrically connected with the metal layer exposed by the opening of the dielectric sub-layer.
Step 9: A photoresist is formed onto the other conductive layer, and the photoresist having at least one opening exposing the other conductive layer.
Step 10: At least other one conductive metal is filled into the opening of the photoresist by, for example, an electroplating process, and the other conductive metal disposed over the other conductive layer.
Step 11: The photoresist is removed.
Step 12: The other conductive layer exposed to the outside is removed by, for example, an etching process, and the other conductive layer deposited under the other conductive metal remains.
Provided that multiple metal layers are to be formed, the sequential steps 7-12 are repeated at least one time.
To achieve the foregoing and other objectives, the present invention provides another process for making the above chip structure. The process for fabricating a chip structure comprises the following steps.
Step 1: A wafer is provided with a plurality of electric devices, an interconnection scheme and a passivation layer. Both the electric devices and the interconnection scheme are arranged inside the wafer. The interconnection scheme is electrically connected with the electric devices. The passivation layer is disposed on a surface layer of the wafer. The passivation layer has at least one opening exposing the interconnection scheme.
Step 2: At least one conductive metal is formed over the passivation layer of the wafer by, for example, a sputtering process, and the conductive metal is electrically connected with the interconnection scheme.
Step 3: A photoresist is formed onto the conductive metal, and the photoresist is patterned to expose the conductive metal to the outside.
Step 4: The conductive metal exposed to the outside is removed, and the conductive metal deposited under the photoresist remains.
Step 5: The photoresist is removed.
Provided that two metal layers are to be formed, the process for fabricating the above chip structure further comprises the following steps:
Step 6: A dielectric sub-layer is formed over the passivation layer and covers the formed conductive metal. The dielectric sub-layer has at least one opening exposing the conductive metal formed at a lower portion.
Step 7: At least other one conductive metal is formed over the passivation layer of the wafer by, for example, a sputtering process, and the other conductive metal electrically is connected with the conductive metal formed at a lower portion.
Step 8: A photoresist is formed onto the other conductive metal, and the photoresist is patterned to expose the other conductive metal to the outside.
Step 9: The other conductive metal exposed to the outside is removed, and the other conductive metal deposited under the photoresist remains.
Step 10: The photoresist is removed.
Provided that multiple metal layers are to be formed, the sequential steps 6-10 are repeated at least one time.
Both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.